Pirfenidone Alleviates Features of Well-Established Chronic Pancreatitis in Mouse Models

Abstract

Abstract Introduction/Objective Chronic pancreatitis (CP) is a fibro-inflammatory disease of pancreas with no targeted therapy and is considered irreversible. Antifibrotic agent pirfenidone is FDA approved for idiopathic pulmonary fibrosis. However, exact molecular mechanism of its action is not clear. The aim of this study was to evaluate pirfenidone as a therapeutic agent for CP. Methods Caerulein-CP was induced in C57BL/6 mice by caerulein injections (50ug/kgx7, i.p., hourly x twice weekly x10 weeks). At 11 weeks, animals were randomized and assigned to either saline or pirfenidone group (400 mg/kg/d by oral gavage for 5 weeks). Mice were euthanized at 17 weeks. L-arginine induced CP was induced by i.p. injections of L-arginine (4.5g/kg x2 hourly, once a week x 4) and treatment was started after 5 weeks of start. Mice were sacrificed at early time-points after starting treatment. Single-cell suspension of pancreata were used for flow- cytometry. Pancreatic atrophy, histology, fibrosis and cytokine mRNA profile were evaluated. In vitro studies were done on stellate cells. Results The treated caerulein-CP mice had improvement in pancreas/mouse weight ratio, (7.03±0.41 vs. 4.75±0.28; p<0.0001). Histology scores and fibrosis markers were reduced. Pancreatic atrophy and histology scores showed significant improvement by day 14 of treatment in L-arginine CP. Flow cytometry showed that by day 7 of treatment there was significant reduction in macrophage infiltration (1.09 ± 0.18 % vs 3.26 ± 0.4 %; p<0.001) and pro-fibrotic M2 macrophage markers [IL-4 (1.5 ± 0.1 % vs 2.8 ± 0.2%; p=0.007)], while M1 marker (MHC II) did not change. mRNA levels of pro-inflammatory and pro-fibrotic cytokines decreased, and of anti-inflammatory cytokines increased. In vitro study on stellate cells showed reduction in mRNA levels of pro-fibrotic and pro-inflammatory cytokines as well as fibrosis markers in treatment group. Conclusion Pirfenidone ameliorates well-established CP in mouse models by altering immune cells.